1. Field of Invention
The present invention relates generally to navigation systems and location-based information delivery, and more particularly, to a method and system for a distributed navigation system wherein a client and a server communicate to carry out distributed navigation tasks.
2. Description of Related Art
Presently, a rapid growth in technological fields such as the personal digital assistant (PDA) and cellular telephones has fueled consumer interest in products that provide on-call real-time guidance and communication. One such technological advance is a navigation system that allows its users to reach destinations by providing turn-by-turn instructions along a calculated route.
Conventional navigation systems are typically satellite-based Global Positioning System (GPS) devices which have been incorporated into automobile navigation systems, for additional information regarding conventional navigation systems, refer to U.S. Pat. Nos. 5,938,720, 5,928,307, 5,922,042, 5,912,635, 5,910,177, 5,904,728, 5,902,350, all incorporated herein by reference. Such conventional automobile navigation systems, however, are expensive and inconvenient to use. Therefore, there is a need to incorporate navigation capabilities so that a user may access real-time turn-by-turn route instructions via personal handheld devices such as a wireless cellular phone or a personal digital assistant (PDA) device.
Several technical obstacles prevent efficient use of navigation systems incorporated into personal handheld devices. One such obstacle is the amount of geographic data needed to provide reasonably detailed navigational information. Small handheld devices comprise limited embedded memory that may not be adequate for storing a large amount of geographic information essential for navigational purposes. This obstacle can be overcome in a distributed navigation system comprising a server-client structure, wherein the navigation functions are partitioned and assigned among one or more distributed servers and the handheld device or client.
Due to limited client memory capacity, conventional distributed navigation systems assign a majority of nominal route calculation tasks to the server, and allocate rerouting calculations almost exclusively to the server. In order to retrieve and display navigation information to the user, the client must frequently communicate with the server. Such constant communication may be time consuming and the information may be inaccurate due to communication delays. Furthermore, the capacities and capabilities of handheld devices or clients are diverse and evolve over time, some devices comprise adequate memory capacity to carry out partial or complete reroute tasks independently of the server.